I have heard of rumors that you can port and polish your intake yourself. I don't know if this is true are not but, I was wondering how to port and polish it myself? Can anyone refer a link or tell me how I can do this?

 

You can only polish the lower runner section on the MEVI, the runner section directly below the butterfly valves. The rest of the runners is not accessible for hand polishing. The lower manifold unit (the part that people don't replace during the MEVI swap...bolts up to the cylinder heads) can be removed and hand polished also. (I've done that.) Takes ~2 hours to do a really good job on that part. I'd imagine it'd take about the same time to do the MEVI lower runner section.

 

what are the benefits?

 

More HP/torque.

 

What did you use to do it yourself?

SuDZ

 

yeah, any help on how to do-it-yourself here would be helpful. I've got two hours spare time and a VI sitting on my floor

 

Since we're on the topic...whats the theory behind this polishing intake manifold thing? I dont understand how it works..somebody please explain? thanks

 

It allow more air in since you widen up the passage ways.

SuDZ

 

Again, anyone know the exact process................

 

You can get books and tools Here but you can use a dremel and some wet sand paper to do a decent job, just don't take off to much or you'll do more harm than good because the ports won't be the same size=turbulance... Btw, I was reading an article on why you Should not polish your intake manifold... something about the airflow can be too smooth, not causing the air/fuel to mix properly, had dyno plots to back it up...

 

Didnt we already talk about this on another thread.

 

You shouldn't port and polish yourself, at least not porting. Polishing is fine if all you're doing is cleaning the area. But to Port properly, you need exact measurements. On a throttle body it doesn't matter since you only have one, but when you start to mess more than one opening, that can be bad for the engine. If you wanna take off the manifolds and clean them with a rag or something fine, it will help airflow as I did it on the Bimmer, after a while, you do get residue or dirt in the manifolds and it helps to clean them up.

 

For hand-polishing the inside of the intake manifold, here's what I recall using:
- 200 grit sandpaper
- 400 grit sandpaper
- Aluminum/mag wheel polish

I used the above in the order listed to gradually remove the casting bumps inside the runners. The final surface was smooth but not shiny...you do no want a mirror-like finish.

Regarding why you shouldn't polish/port, that only applies to runners/ports that will see a fuel/air mixture. You WANT surface roughness in those areas to add turbulence to the walls to keep the fuel from collecting on the surface. On the Maxima, you're safe polishing the upper intake manifold piece as well as the lower manifold piece. The injector sits at the bottom of the lower piece, thus only the intake ports in the cylinder heads actually see a fuel/air mixture. The intake manifold pieces never see fuel.